Dielectric heating unit



p i 1952 w. H. ANDERSON ETAL 2,593,959

DIELECTRIC HEATING UNIT Filed March 1, 1949 v 3 Sheets-Sheet l a 24 WITNESSES: #1 INVENTORS a l I I Hf. William H.Anderson,Deon S.Shingler,

8 Bruce Boyd.

7 Generating v Equipment 26(1- A- W aa I186 20 ATTO R N EY April 22, 1952 w. H. ANDERSON ET AL 2,593,959

DIELECTRIC HEATING UNIT Filed March 1, 1949 5 Sheets-Sheet 2 l 9 2. ,uo I 84 I I l 80 l m 74 I60 I44 l24'l40 k 70 88 75 1 27 152 I20 I42 I54 I4 34 5o 36 I 40 25 32 INVENTORS |45 William H.Anders0 n, Dean S. Shingler W i 6 a a y ATTO RN EY Ap 1952 w. H. ANDERSON ET AL 2,593,959

DIELECTRIC HEATING UNIT Filed March 1, 1949 5 Sheets-Sheet 3 E ML:

l2l 72 e WITNESSES: INVENTORS a l a William H. Anderson, Deon S. Shingler,

GBBruce Boyd. Y Y

ATTORNEY Patented Apr. 22, 1952 UNITED STATES ATENT OFFICE DIELECTRIC HEATING UNIT Wiiliam H. Anderson, Elkridge, and Dean S. Shingler and Bruce Boyd, Baltimore, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 1, 1949, Serial N 0. 78,902

11 Claims. 1

Our invention relates to small dielectric heating units of a type for dielectrically heating small objects.

Such a unit usually comprises an outer metal casing which contains the electronic tubes and high-frequency circuits which produce the highfrequency electrical energy needed for the dielectric heating. The high-frequency energy produced inside the casing is fed to two relatively insulated heating-electrodes carried by the top wall of the casing. The heating-electrodes are usually two small parallel plates which are arranged one above the other so that they provide a work-receiving space between them. The usual unit also comprises a two-member protective metallic cage which encloses or surrounds the heating-electrodes. One of the cage-members is hinged or otherwise raisable with respect to the other cage-member so that the cage can be readily opened and closed to provide easy access to the interior of the cage. Generally the raisable cage-member carries one of the heating-electrodes. At present, to the best of our knowledge, each, self-contained unit of the type described is provided with a single cage only, and its capacity for heat-treatin objects is correspondingly limited.

An object of our invention is to increase the capacity of a small self contained dielectric heating unit of the type described by providing it with two independently-operable cages, each of which has a pair of heating-electrodes between which work can be dielectrically heat-treated.

A further object of our invention is to provide a way of modifying existing small dielectric hea ing units of the type described so as to provide them with a plurality of dielectric heating cages instead of the single cage at present provided. Consequently, the production ofsuch units can be greatly increased at a small expense.

In the application of our invention to present models of dielectric heating units, we cut additional holes in the top wall of the casing of the unit and superimpose another wall which carries a pair of separated cages. Each cage contains its can pair of relatively insulated heatingelectrodes; and the added structure includes a transfer-switch mechanism by means or" which the single high-frequency supply inside the casing can be connected to and disconnected from the heating-electrodes in the several cages in a predetermined manner. Consequently, either cage may be unloaded and reloaded while the other is closed and in its heating period. Additionally, the added structure contains a safety feature, operated by the switch mechanism, which prevents the application of high-frequency energy to the heating-electrodes of an opened cage.

In accordance with specific details of our invention, which we consider new and useful in and of themselves, a dielectric heating unit embodying our invention comprises a single switch-operating handle or operating member that passes through a wall of the casing of the unit. This handle selectively connects high-frequency energy to the heating-electrodes inside a cage of a twocage unit, and at the same time grounds the heating-electrodes in the other cage of the unit.

Features, innovations and advantages of our invention, in addition to the foregoing, will be discernible from the following description of an embodiment thereof which is preferred at the present time. This description should be taken in conjunction with the accompanying drawings. In the drawings, which are on varying scales:

Figure 1 is a perspective view of the upper part of a self-contained dielectric heating unit embodying our invention.

Fig. 2 is a partial vertical sectional view along the length of the unit;

Fig. 3 is a vertical sectional View substantially on the line III-III of Fig. 2;

Figs. 4 and 5 are horizontal sectional views substantially on the lines IV-IV and V-V, respectively, of Fig. 2;

Fig. 6 is a perspective view of a structurallyindependent item of our invention, and

Fig. 7 is a schematic wiring diagram of the electrical connections utilizable in a unit embodying our invention.

While our invention can be incorporated in a separately designed unit, we prefer to incorporate it into existing designs and hence our invention is described in connection with the latter.

Referring more particularly to Figs. 1 and 3 of the drawings, a small portable dielectric heating unit comprises an outer metallic casing 2 consisting of suitably assembled walls. The walls comprise a front wall 4 with a slope panel section 6, opposite end walls 8 and H), a back Wall l2 and a horizontal upper wall 14 secured to the upright walls 4, 8, l and 2. The casing 2 contains the necessary electronic tubes, circuits and adjustable mechanism for generating energy at the desired high frequency. The generating equipment is supplied with commercially available power through a pair of conductors that can be connected to any suitable commercial power outlet. (In Fig. '7 the high-frequency generating parts are indicated collectively by a block IS. The generating-equipment is of the tube-oscillator type. The low-voltage low-frequency conductors which supply energy to the generating equipment are indicated at 18 and 2B. The highfrequency energizing circuit of the tube-oscillation generator comprises agrounded conductor 22 and an insulated conductor 24.)

In a conventional unit, the upper wall [4 would ordinarily be the outer top wall of the casing 2. For modifying such a conventional unit so that it embodies our invention, this wall I4 receives a structure which carries two metallic heating cages instead of the conventional single cage. To this end the wall I4 is provided with openings for the insulated heating-electrodes for the cages and for a switch-shaft of a transfer-switch that controls the energization of the heating-electrodes. Such holes are indicated in Fig. 2 as comprising a shaft-hole 25, and electrode-holes 2i and 29, one on each side of the shaft-hole 25. With the upper wall l4 perforated along the lines described, two sub-structures are secured to the' casing, one below and one above the upper wall [4.

The lower sub-structure, shown more particularly in Figs. and 6, comprises a framework Sll of insulating material. The framework 36 comprises a base plate 32, a securing plate 34 and posts 36 holding the plates together in parallel planes. The base plate 32 carries a double-throw transfer switch which comprises a movable contact in the form of a knife blade 38, and a pair of stationary switch contacts 40 and 42. The movable contact or knife blade 38 is centrally pivotally supported between the stationary contacts 40 and 42 by a pivot means on the base plate 32. The pivot means comprises a metal pivot 44. The knife blade 38 is twisted about its pivot through an insulating linkage which comprises links 46 and 48. The latter carries a socket 561 at its end. Operating means, described later, can turn the socket 50 about its own axis so that the linkage comprising the links t6 and 48 will twist the knife blade 38 one way or the other depending on the direction in which the socket 50 is turned; and this knife blade can be made to selectively engage the stationary contact 49 or the stationary contact 42. In Fig. 5 it is shown in a position engaging the contact 46 and out of engagement with contact 42; and in Fig. 6 it is shown in the reverse position.

The metal pivot 44 extends below the base plate 32 and is conductively directly connected to the insulated high-frequency energy supply conductor 24 inside the casing 2. Depending on its position, the movable contact or knife blade 38 completes a circuit from this insulated highvoltage high-frequency conductor 24 to either of the stationary contacts t0 and 42. Removably secured to the contacts 46 and 42 are ends of inductance coils 55 and 58 respectively.

The foregoing lower sub-structure is independently carried by the upper Wall M by securing the top of its securing plate 34 to the underside of the upper wall. Consequently, the transfer switch mechanism and the inductance coils 56 and 58 are carried inside the casing. The remaining ends of the inductance coils 56 and 58 lie under the electrode-holes 2i and 2?! respectively. These ends of the inductance coils 56 and 58 are removably attached to stiff upright conductors 69 and 82, respectively, of the upper sub-structure.

The upper sub-structure is outer side of the inner wall i shallow dished metal member M. This men: ber 64 has a, back wall 6%, end walls 63 and i i, and a front wall 12. The end walls 63 and Eli are provided with flanges that rest on the end Walls 8 and ll) of the casing 2. The member es has a generally flat upper or top wall Hi which is parallel to the upper wall Hi of the casing 2. Consequently, the upper wall it becomes an inner upper wall for the casing 2 and the upper wall 14 becomes an outer upper wall or top wall for the casing 2.

As shown in Fig. 2, top wall 14 of the upper sub-structure member 64 has a pair of openings 15 and Tl which are vertically in line with the holes 21 and 29, respectively, in the inner wall l4. On its upper side, the upper wall it carries a pair of short insulating tubes 86 and 82 of insulating material, these tubes being respectively in line with and about the holes 15 and El. The tubes and 82 respectively carry insulated heating-electrodes 84 and 85, the heating-electrodes being metal plates. The stiff conductors 60 and 62 are secured to the center of the heat ing-electrodes B4 and 86, respectively, and are air-insulated from the walls of the casing by the holes 21 and 15, and 29 and H, respectively. Secured to the lower side of the upper wall it are short spacer tubes 88 and 93 which are coaxial with, but of larger diameter than, the holes 21 and i5, and 29 and il, respectively. The stiif conductors Bil and 82 pass through the associated surrounding tubes and extend below the inner upper wall 14 so that the inductance coils 56 and 58, which they removably carry are suspended inside the casing with adequate air insulation completely around the corn ductors and the coils.

The upper top wall 74 of the upper sub-structure of the casing 2 carries two metal cages $2 and 94, with the cage 92 about the heating-electrode 84 and the cage 94 about the heating-electrode 86. The cage 92 comprises a lower cagemember 96 fixed to the top of the upper top wall 14 and an upper cage-member 98 hinged to the back end of the lower cage-member 96. The hinged member 98 carries a handle 95 so that it can be easily raised or lowered. Similarly, the cage 94 comprises a lower cage-member tea, a hinged upper cage-member I64 and a handle I06.

The hinged cage-members $3 and W4 carry heating-electrodes H0 and H2, respectively. These electrodes are solidly electrically grounded or connected to the metal casing z in any suitable way common to the art so that a high-frequency circuit is completed directly, or through the easing, to the other high-frequency supply conductor 22, shown in Fig. '7. Such grounding means for each of the electrodes H9 and H2 comprises a copper strap *6. When a cage 92 or 94 is closed, its heating-electrodes are spaced for dielectrically heating work therebetween, in

a normal manner.

The bottom side of the upper top wall it of secured to the and comprises a the upper sub-structure also carries a means for controlling the electrical energization or potentials of the pairs of heating-electrodes 84 and I I5, and 86 and I I2. Referring more particularly to Figs. 14, this means comprises a manually operable switch-operating arm I for operating the transfer switch shown in Fig. 5, and for operating a selective grounding means for the insulated heating-electrodes 84 and 85. The arm I20 extends outwardly through a vertical hole IZI in the front wall 12 of the dished member 64, and is provided with a knob I22. The switch arm I can be oscillated to the right or left about a pivot I24. The arm I25 can be frictionally held or latched in either of its extreme positions.

The pivot I24 for the arm or handle IE5 is rotatably carried in av frame secured to the underside of the upper top wall 14.

and pillars I44. The bottom plate I42 rests on the upper wall I4 and covers the hole 25 therein. The pivot I24 has a section of smaller diameter which passes downwardly below the plate I 42 and fits into the socket to of the transfer switch mechanism shown in Fig. 6. A set screw I46, or the equivalent, ties the socket to the pivot I24 so that both rotate together upon movement of the handle or arm I20.

As shown more clearly in Fig. 4, the arm I20 extends backwardly beyond the pivot I24 to provide a fork I59 to the legs of which are pivoted a pair of grounding bars or rods I 52 and I54. The rod I52 moves through an enlarged hole I in the tube 88; and the rod I54 moves through a similar hole I51 in the tube 96; these holes being in the nature of guiding means directing a rod I52 or IE4 against an insulated conductor 56 or 62, as the case may be. The rods I52 and I54 are metallic; and spring contacts 55 and I52, respectively, rub against them. These spring contacts I50 and !'52 are solidly grounded to the casing 2 and serve as a further precaution for insuring that the rods are grounded at all times.

Also attached to the lower side of the top wall E4 of the upper sub-structure, on opposite sides f the arm member 26, are a pair of normally opened switches I54 and IE5.

The operation of the equipment described is as follows: When the switch arm or handle I20 is moved to the left, with respect to Fig. its rotatable pivot I24 to which the arm is rigidly secured, turns the socket 58 so that the linkage d8, :38 throws the knife ment with the contact 56 and out of engagement with the contact '32, as shown in Fig. 5. The high-voltage high-frequency conductor 24 is thereby connected to the contact 45 so that highirequency voltage is applied to the insulated heating-electrode 54 via the inductance coil 55 and the stifi conductor 55. When the arm or handle E2!) is so moved to the left, it also moves the grounding rod I52 away from the stiff conductor E5 while moving the other grounding rod 55% into electrical engagement with the stiff conductor 52 that is attached to the insulated heating-electrode 36. Consequently, the insulated heating-electrode 88 will be at ground potential, and the cage 94 can be opened and work placed on this heating-electrode with safety.

After the cage 94 is closed, the arm E25 can be swung to the right. Such movement causes the knife blade 38 to disengage the contact 40 and This frame com-- prises a top plate I45, a bottom thrust plate I42 blade 83 into engagecontrolled switch H2.

to engage the contact 62, as shown in Fig. 6. This movement also moves the rod I54 from the stiff conductor 52 and moves the rod I 52 into engagement with the stiff conductor 65. Accordingly, the high-voltage high-frequency supply on the conductor 24 can pass to the insulated heating-electrode 86 via the pivot 44, knife blade 38, the stationary contact 42, the inductance coil 53 and the stiff insulated conductor 62. In the meantime, the heating-electrode 84 is grounded to the casing 2 via the stiff insulated conductor Eli, the grounding rod I52 and the spring Ififi. Accordingly, the cage 92 can be opened, the work heated therein removed and new work placed on the heating-electrode 84. In this way the cages 92 and 9e are successively used; one of them heat-treating an object while an operator is reloading the other one.

The time interval consumed in switching is very small. On an integrated basis, the preferred embodiment of the invention permits an operator to use his time most advantageously, and permits the high-frequency generating equipment to be in operation almost continuously, being interrupted momentarily by the switching operation. The grounding of the unused insulated heating-electrode i important. At the high-frequencies used, the short path to ground prevents voltages which otherwise would appear on the unused heating-electrode and its connections through capacity coupling.

Fig. '7 shows utiiizable electrical connections in a dielectric heating unit embodying our invention. Primarily power for the unit comes through the low voltage leads !8 and 20. The high-frequency generating equipment It comprises a transformer having a primary winding I236 which can receive power from the lines I8 and 28 through either of two branch circuits I88 and I99. The branch circuit 83 includes a switch H32 and the switch 53 in series, both of these switches being normally spring biased to open position. The branch circuit 96 includes a switch 19-5 and the switch Ie l in series, both of these switches also being normally spring biased to open position. The switches {92 and :94 are attached to the cages 92 and 94, respectively. Each of the switches i532 and i5 3 move to open position when its associated cage is being opened and remains open as long as the cage i open. Fig. 7 schematically shows the cage member 98 of the cage 52 in closed position closing the switch I S4 in the branch circuit I90. The cage 84 i shown open. so that its cagemeinber M14 is away from the switch 592, and the latter is open.

When the arm or handle 28 is moved to the left, the knife blade or movable contact 33 en gages the stationary contact ll At the same time the arm or handle i29 closes the normally opened switch 54. Consequently, the branch circuit I9 3 is completed and high-frequency energy is available across the heating-electrodes 84 and I it? inside the closed cage 92. The branch circuit I38 for the cage es is opened at two places, at the arm controlled switch I56 and at the cage The insulated heatingelectrode of the cage 8 is grounded through the rod 54; and the other heating-electrode H2 of the cage 9:1 is grounded permanently.

When the cage s4 is closed and the handle 529 is moved to the right, the grounding rod I54 leaves the conductor 52 and the grounding rod I52 grounds tr e conductor ES. The tube oscillation generator equipment will now be energized through the branch circuit I83 instead of the branch circuit I99, and high-frequency energy will be on the conductor 62.

While we have described our invention in its preferred form, it is obvious that the principles thereof can be embodied in a dielectric heating unit of a type described in ways other than that described as the preferred embodiment.

We claim as our invention:

1. A dielectric heating unit comprising a metallic'casing adapted to contain high-frequency generating equipment, said casing having a pair of spaced generally horizontal upper walls, a plurality of metallic cages carried by said casing over said upper walls, each cage comprising separable cage-members, a heating-electrode inside each cage, a high-frequency upply comprising an insulated conductor inside said casing, below said upper walls, and circuits and switching means carried by and between said upper walls comprising horizontally operable switch means for selectively connecting said insulated conductor to one of said heating-electrodes.

2. A dielectric heating unit comprising a metallic casing adapted to contain high-frequency generating equipment, said casing having a pair of spaced generally horizontal upper walls, a plurality of metallic cages carried by the top one of said upper walls, each cage comprising separable cage-members, a heating-electrode inside each cage, a high-frequency supply comprising an insulated supply conductor inside said casing, below said upper walls, and circuits and switching means carried by and between said upper walls comprising operable switch means for connecting said insulated supply conductor to a selected one of said heating-electrodes, said switch means comprising grounding means between said spaced upper walls for grounding the remaining ones of said heating-electrodes, said switch means and said grounding means being operable by a control member which extends from said casing.

3. An invention including that of claim 2 but further characterized by said switch means comprising a separate stationary contact for each heating-electrode and movable contact-means operated by said control member and selectively engageable with said contacts, said contacts and contact-means being carried by the lower one of said upper walls, and said grounding means comprising movable groimding bars between said upper walls.

4. An addition for increasing the capacity of a dielectric heating unit comprising: a metallic wall means having a generally horizontal wall, a pair of metallic cages carried on the top of said wall, each of said cages comprising a pair of separable cage-members, an insulated heatingelectrode in each cage, an insulated conductor extending downwardly from each heating-electrode, and passing through openings in said wall, movable bars selectively horizontally movable into engagement with said insulated conductors, guide means under said wall slidably carrying said bars, said bars being electrically connected so as to be at the potential of said wall, and.

gearing comprising a pivoted member and handle therefor for moving said bars.

5. An invention including that or claim 4 in further combination with a pair of stationary contacts inside said casing carried by said wall means, circuit means connecting said insulated conductors separately to said stationary contacts, a movable contact carried by said wall means selectively engageable with said stationary contacts, interconnecting mechanical means on said movable contact adapted to be fastened to said pivoted member, whereby said handle can be 5 used to move said movable contact and said bars simultaneously.

6. A dielectric heating unit of a type described comprising a metallic casing adapted to contain high-frequency generating equipment, said casing having a pair of spaced generally horizontal upper walls, a plurality of metallic cages carried by the top one of said upper walls, each cage comprising separable cage-members, an insulated heating-electrode inside each cage, an insulated conductor extending downwardly from each of said heating-electrodes and passing through holes in said walls, a pair of horizontally movable grounding bars movably supported between said -walls, each bar being adapted to engage and disengage an associated one of said insulated conductors, a pair of stationary insulated contacts carried inside said casing under said walls, said contacts being horizontally separated, a connection from each of said contacts to one of said conductors, a contact-engaging switch-blade insulatedly supported under said walls, and pivoted to turn on a vertical axis into engagement with one or the other of said contacts, said generating equipment comprising an insulated supply conductor connected to said switch-blade, and handle means extending outside said casing, for operating said bars and switch-blade.

'7. A high-frequency heating unit of a type described comprising a metallic casing adapted to contain high-frequency generating equipment providing an insulated supply conductor, said casing having wall means including a horizontally-extending top wall, a plurality of individual work-receiving members carried by said top wall, 40 said top wall .having a pair of openings below said work-receiving members, an insulated conductor extending downwardly from each of said work-receiving members and passing through one of said holes, horizontally movable grounding means, supporting ,means movably supporting said grounding means in said casing for selectively grounding said conductors, a pair of stationary insulated contacts supported in said cas ing, said contacts being horizontally displaced, a connection from each of said contacts to one of said conductors, a contact-engaging switchblade, supporting means insulatedly pivotally supporting said switch-blade in said casing to turn on a vertical axis for selectively engaging said contacts, said switch-blade being connected to said supply conductor, and handle means extending outside said casing for operating said grounding means and switch-blade.

8. A high-frequency heating unit as defined in claim 7 but further characterized by said sup porting means supporting said grounding means and switch-blade so that they are in adjacent levels immediately under said top wall.

9. A high-frequency heating unit as defined in claim 7 but further characterized by said supporting means comprising a supporting frame carried immediately under said top wall.

10. A high-frequency heating unit as defined in claim '7 but further characterized by said grounding means comprising horizontal bars lo cated between a pair of said connection conductors and adapted to ground one or the other thereof.

11. A high-frequency heating unit as defined in claim 7 but further characterized by each of 9 said work-receiving members comprising an insulated dielectric heating-electrode, a cage about each of said heating-electrodes, and said con- 2: nections comprising an inductance coil under 2,401,277 the associated conductor. 5 4 9 3 7 WILLIAM H. ANDERSON. 2,442,451 DEAN S. SHINGLER. 2 452,3 5 BRUCE BOYD. 2 512 751 REFERENCES CITED 10 The following references are of record in the file of this patent:

1 UNITED STATES PATENTS Name Date Dravneek June 8, 1943 Stratton May 28, 1946 Zottu Apr. 22, 1947 Albin June 1, 1948 Frederick Oct. 26, 1948 Proctor et al June 27, 1950 OTHER REFERENCES H F Heat Laboratory, Electronic Industries, November 1946, pages 62 and 63. 

